The present invention relates to a method for fabricating a semiconductor device including a capacitor device using a ferroelectric or high dielectric of a metal oxide as a capacitor dielectric film.
A capacitor device including, as a capacitor dielectric film, a ferroelectric film or a high dielectric film made of a metal oxide has remnant polarization derived from its hysteresis characteristic and a high dielectric constant. Therefore, such a capacitor device has been used instead of a conventional capacitor device including a capacitor dielectric film of silicon oxide or silicon nitride in the field of nonvolatile memories and DRAMs.
In order to form a capacitor device on one semiconductor substrate (wafer), a plurality of fabrication procedures should be performed, and therefore, a semiconductor substrate under fabrication is generally contained in a plastic container during a convey time when the semiconductor substrate is being conveyed between a plurality of fabrication systems or a wait time before or after the conveyance.
The present inventor has found the following problem in a conventional method for fabricating a semiconductor device including a capacitor device using a ferroelectric or a high dielectric:
An interlayer insulating film formed between a capacitor device and an interconnect layer on a semiconductor substrate absorbs atmospheric moisture during the convey time or the wait time between one procedure and another subsequent procedure, and the absorbed moisture degrades the electric characteristic of the capacitor dielectric film. The cause of this problem will now be described.
FIG. 11 shows the dependency on the annealing temperature of the remnant polarization value and the breakdown voltage value of a conventional capacitor device including a ferroelectric as a capacitor dielectric film. In this case, with an interconnect formed above the capacitor device, an interlayer insulating film of silicon oxide obtained by causing a reaction between ozone (O3) and TEOS (tetraethyl orthosilicate) at the atmospheric pressure (namely, ozone TEOS) is formed, and annealing is performed in an oxygen atmosphere at a temperature of 300xc2x0 C., 350xc2x0 C. or 400xc2x0 C.
As is understood from FIG. 11, when the annealing is performed at 400xc2x0 C., both the remnant polarization value and the breakdown voltage value are lowered.
FIG. 12 shows the dependency on the heating temperature of the concentration of moisture desorbed from silicon oxide obtained by thermal desorption spectroscopy (TDS). As is understood from FIG. 12, when the heating temperature for a semiconductor substrate exceeds 200xc2x0 C., moisture desorbed from silicon oxide is observed, and the peak of the moisture concentration is found at 400xc2x0 C. regardless of the substrate temperature.
These facts seem to reveal the following: The interlayer insulating film made of ozone TEOS absorbs the atmospheric moisture during the convey time or the wait time, and the absorbed moisture is easily desorbed and hence is reacted with the ferroelectric through the subsequently performed annealing, resulting in lowering the remnant polarization value.
On the other hand, however, in order to improve the yield and the reliability of a semiconductor device, it is necessary to perform annealing and form a protection film at a high temperature for recovering a damage caused in forming an interconnect and for preventing corrosion of aluminum.
The present invention was devised to overcome the above-described conventional problem, and an object is preventing the electric characteristic of a capacitor dielectric film including a ferroelectric of a metal oxide from being degraded by moisture desorbed from an interlayer insulating film through annealing.
In order to achieve the object, according to a method of this invention for fabricating a semiconductor device including a capacitor device having a capacitor dielectric film of a metal oxide, an interlayer insulating film of an oxide is prevented from including moisture during a convey time or a wait time before a subsequent step.
Specifically, the first method for fabricating a semiconductor device of this invention includes a first step of forming, on a substrate, a capacitor device including a capacitor dielectric film of a metal oxide; a second step of depositing an interlayer insulating film of an oxide on the capacitor device; and a third step of forming an opening in a region of the interlayer insulating film disposed above the capacitor device and forming, on the interlayer insulating film, a conducting film connected to the capacitor device through the opening in such a manner that a portion of the interlayer insulating film disposed above a periphery of the capacitor device is exposed, and during a convey time when the substrate on which the conducting film has been formed is being conveyed from the third step to a following forth step or during a wait time before or after conveying the substrate from the third step to the fourth step, the substrate on which the conducting film has been formed is contained in a container an atmosphere within which has a lower moisture concentration than the ambient atmosphere until a substantially whole top face of the interlayer insulating film is covered with another member.
In the first method for fabricating a semiconductor device, the amount of moisture absorbed from the air by the interlayer insulating film formed on the substrate during the convey time or the wait time is reduced. Therefore, even when annealing is performed in a subsequent step, the annealed interlayer insulating film minimally desorbs moisture, resulting in preventing electric characteristic degradation of the capacitor dielectric film derived from reduction or the like of the capacitor dielectric film including a ferroelectric or the like of a metal oxide.
In the first method for fabricating a semiconductor device, a barrier film made from the conducting film is preferably formed in the third step.
In this case, an interconnect formation film corresponding to the another member is preferably deposited over the interlayer insulating film including the conducting film in the fourth step.
In the first method for fabricating a semiconductor device, an interconnect made from the conducting film is preferably formed in the third step.
The first method for fabricating a semiconductor device preferably further includes, after the fourth step, a fifth step of performing annealing on the conducting film at a temperature of approximately 200xc2x0 C. or more. Thus, annealing for recovering damage having been caused in patterning the capacitor dielectric film or the conducting film can be definitely performed.
In the first method for fabricating a semiconductor device, the interlayer insulating film is preferably made of silicon oxide.
In the first method for fabricating a semiconductor device, the conducting film is preferably a single-layer film made of one of or a multilayer film including at least two of titanium, titanium nitride, aluminum, tungsten and copper.
The second method for fabricating a semiconductor device of this invention includes a first step of forming, on a substrate, a capacitor device including a capacitor dielectric film of a metal oxide; a second step of forming a first interlayer insulating film on the capacitor device; a third step of forming, on the first interlayer insulating film, a first conducting film electrically connected to the capacitor device; a fourth step of forming a second interlayer insulating film of an oxide on the first interlayer insulating film including the first conducting film; and a fifth step of forming a second conducting film on a substantially whole top face of the second interlayer insulating film, and during a convey time when the substrate on which the second interlayer insulating film has been formed is being conveyed from the fourth step to the fifth step or during a wait time before or after conveying the substrate from the fourth step to the fifth step, the substrate on which the second interlayer insulating film has been formed is contained in a container an atmosphere within which has a lower moisture concentration than the ambient atmosphere.
In the second method for fabricating a semiconductor device, the amount of moisture absorbed from the air by the second interlayer insulating film formed on the substrate during the convey time or the wait time is reduced. Therefore, even when annealing is performed in a subsequent step, the annealed second interlayer insulating film minimally desorbs moisture, resulting in preventing electric characteristic degradation of the capacitor dielectric film derived from reduction or the like of the capacitor dielectric film including a ferroelectric or the like of a metal oxide.
The second method for fabricating a semiconductor device preferably further includes, after the fifth step, a sixth step of performing annealing on the second conducting film at a temperature of approximately 200xc2x0 C. or more.
In the second method for fabricating a semiconductor device, the first interlayer insulating film or the second interlayer insulating film is preferably made of silicon oxide.
In the second method for fabricating a semiconductor device, each of the first conducting film and the second conducting film is preferably a single-layer film made of one of or a multilayer film including at least two of titanium, titanium nitride, aluminum, tungsten and copper.
The third method for fabricating a semiconductor device of this invention includes a first step of forming, on a substrate, a capacitor device including a capacitor dielectric film of a metal oxide; a second step of forming an interlayer insulating film of an oxide on the capacitor device; a third step of forming an interconnect of a conducting film on the interlayer insulating film; and a fourth step of forming a protection film of a nitride on a substantially whole top face of the interlayer insulating film including the interconnect, and during a convey time when the substrate on which the interlayer insulating film and the interconnect have been formed is being conveyed from the third step to the fourth step or during a wait time before or after conveying the substrate from the third step to the fourth step, the substrate on which the interlayer insulating film and the interconnect have been formed is contained in a container an atmosphere within which has a lower moisture concentration than the ambient atmosphere.
In the third method for fabricating a semiconductor device, the amount of moisture absorbed from the air by the interlayer insulating film formed on the substrate during the convey time or the wait time is reduced. Therefore, even when annealing is performed in a subsequent step, the annealed interlayer insulating film minimally desorbs moisture, resulting in preventing electric characteristic degradation of the capacitor dielectric film derived from reduction or the like of the capacitor dielectric film including a ferroelectric or the like of a metal oxide.
The third method for fabricating a semiconductor device preferably further includes, between the third step and the fourth step, a step of performing annealing on the interconnect at a temperature of approximately 200xc2x0 C. or more.
In the third method for fabricating a semiconductor device, the interlayer insulating film is preferably made of silicon oxide.
In the third method for fabricating a semiconductor device, the protection film is preferably made of silicon nitride.
In the third method for fabricating a semiconductor device, the conducting film is preferably a single-layer film made of one of or a multilayer film including at least two of titanium, titanium nitride, aluminum, tungsten and copper.
The fourth method for fabricating a semiconductor device of this invention includes a step of forming, on a substrate, a capacitor device including a capacitor dielectric film of a metal oxide, and during a convey time when the substrate on which the capacitor device has been formed is being conveyed to a subsequent step following the step of forming a capacitor device or during a wait time before or after conveying the substrate from the step of forming a capacitor device to the subsequent step, the substrate on which the capacitor device has been formed is contained in a container an atmosphere within which has a lower moisture concentration than the ambient atmosphere.
In the fourth method for fabricating a semiconductor device, even when annealing is performed in a subsequent step, the electric characteristic of the capacitor dielectric film including a ferroelectric or the like of a metal oxide can be prevented from being degraded by moisture.
In any of the first through fourth methods for fabricating a semiconductor device, the container is preferably hermetically sealable and loaded with a moisture absorption material.
In this case, the moisture absorption material is preferably made of silica gel or active alumina.
In any of the first through fourth methods for fabricating a semiconductor device, the container is preferably hermetically sealable and filled with an inert gas or kept evacuated.
In this case, the inert gas is preferably nitrogen, argon or helium.
In any of the first through fourth methods for fabricating a semiconductor device, the metal oxide is preferably a layered perovskite composite oxide including bismuth or a perovskite composite oxide including lead, zirconium and titanium, or strontium and titanium.